Petrogenesis of the Neoproterozoic bimodal volcanic rocks along the western margin of the Yangtze Block： New constraints from Hf isotopes and Fe/Mn ratios

• Published in: Chinese science bulletin Vol. 50; no. 21; pp. 2481 - 2486
• Main Author: LI Xianhua QI Changshi LIU Ying LIANG Xirong TU Xianglin XlE Liewen YANG Yueheng
• Format: Journal Article
• Language: English
• Published: Graduate University of Chinese Academy of Sciences, Beijing 100039, China%Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 01.11.2005; Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China%Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
• Subjects: 同位素; 岩石学; 火山岩; 玄武岩; basalt; Neoproterozoic; Fe/Mn; Hf isotope; mantle plume; rhyolite; Yangtze Block
• ISSN: 1001-6538; 1861-9541
• DOI: 10.1360/982005-287

High-precision major element and Hf isotope data are reported for the Neoproterozoic Suxiong volcanic rocks along the western margin of the Yangtze Block. These volcanic rocks have variable εHf（T） values and Fe/Mn ratios. The relatively primitive basalts have high Fe/Mn ratios and high Hf-Nd isotopic compositions, indicating that they were generated by partial melting of garnet clinopyroxene in mantle plume at high pressure. Thus, the Suxiong basalts are genetically related to the proposed Neoproterozoic superplume. On the contrary, a few differentiated basalts have low Fe/Mn ratios and low Hf-Nd isotopic compositions. They are likely to experience assimilation-fractional crystallization process. The Suxiong rhyolites have consistent Hf and Nd model ages of 1.3-1.4 Ga. They are likely generated by shallow dehydration melting of pre-existing young arc igneous rocks associated with the basaltic underplating/intrusion in a continental rift.